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Transform arc segments


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Hello, i create lisp for transform *line, circle, arc ... and the question is:

How to transform arc without convert it to polyline.

Or how to covert arc to polyline transform vertex (this method work fine) and convert again to arc (i don't know how to convert again to arc).


What i do, have a lot of math to coordinate system 1 --> coordinate system 2, when i covert vertex of lines everything work perfect but with arcs don't know how to transform vertex clear.

This is about my dissertation.


Thank you :)

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Hello i attach .dwg, but this post are much different. For the first post i solve the problem alone and i think i can solve this to but its more harder.


Edited by Trudy
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Its always good to follow up  even just to say "I figured it out"


Arc's don't have end points. in dxf code format like lines do.

(-1 . <Entity name: 38277240>) 
(0 . "ARC") 
(5 . "697F") 
(330 . <Entity name: 381a1a60>) 
(100 . "AcDbEntity") 
(67 . 0) 
(410 . "Model") 
(8 . "0") 
(62 . 1) 
(370 . -1) 
(100 . "AcDbCircle") 
(10 330578.878812906 4986801.45718755 0.0) 
(40 . 312945.883966499) 
(210 0.0 0.0 1.0) 
(100 . "AcDbArc") 
(50 . 4.71238546667679) 
(51 . 4.99139637837235) 


10 is the center point.

40 is the radius

50 is the start angle in radian

51 is the end angle in radian


I was looking to do the same thing.

Rather then calculate where to move the end points I opted to create a circle using the selected arc's center point and radius

Delete the original arc and then trim the circle to where I needed endpoints to create an arc again.


(defun C:AE (/ arc cen rad)
  (setq arc (entget (car (entsel "\nSelect Arc"))))
  (setq cen (assoc 10 arc)))
  (setq rad (assoc 40 arc)))
  (entmake (list (cons 0 "CIRCLE") cen rad)))
  (entdel (cdr (assoc -1 arc)))



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